Hold your breath: peripheral and cerebral oxygenation during dry static apnea.

Abstract

Acute breath-holding deprives the human body from oxygen. In an effort to protect the brain, the diving response is initiated, coupling several physiological responses. The aim of this study was to describe the physiological responses to apnea at the cardiac, peripheral and cerebral level. 31 physically active subjects (17 male, 14 female, 23.3 ± 1.8years old) performed a maximal static breath-hold in a seated position. Heart rate (HR), muscle and cerebral oxygenation (by means of near-infrared spectroscopy, NIRS) were continuously measured. RM MANOVA's were used to identify changes in HR, peripheral (mTOI) and cerebral (cTOI) tissue oxygenation and oxygenated (O2Hb) and deoxygenated (HHb) hemoglobin during apnea. Average apnea duration was 157 ± 41s. HR started decreasing after 10s (p < 0.001) and dropped on average by 27 ± 14bpm from baseline (p < 0.001). mTOI started decreasing 10s after apnea (p < 0.001) and fell by 8.6 ± 4.0% (p < 0.001). Following an immediate drop after 5s (p < 0.001), cTOI increased continuously, reaching a maximal increase of 3.7 ± 2.4% followed by a steady decrease until the end of apnea. cTOI fell on average 5.4 ± 8.3% below baseline (p < 0.001). During apnea, the human body elicits several protective mechanisms to protect itself against the deprivation of oxygen. HR slows down, decreasing O2 demand of the cardiac muscle. The decrease in mTOI and increase in cTOI imply a redistribution of blood flow prioritizing the brain. However, this mechanism is not sufficient to maintain cTOI until the end of apnea.